I'm just rounding to whole numbers so I'm considering 13 agil == 1% crit.
Using 60 stat weights for raiding (str = 2, agi = 1.17) and adjusting agility's weight it to 39 (13 == 20, 1.93 == 1.17) you can see that str still provides a higher, albeit not by much, dps increase.
They're so close...